What's the big point about Tengu/Fat Devil Jin? xD
He is just a boss in DOA2 and DOAD and a bonus character in DOA4. He already dead, so stop thinking TN will add him because they will not. Same for Ein, he is just a bonus character, in my opinion, it was pretty okay to have him in DOA3, but in DOA4 he was unnecesary because he is Hayate, and Hitomi was his replacement wich have a very similar moveset. You have to look at TN side. They get ride of Leon and Ein at the start because they wanted space for Mila and Rig, that´s mean they want to add more original character instead of bring back the old bonus ones. They bring us back Leon because fans criticized so much his absence and because he is a original character and not a bonus like the other two.
Don´t get me wrong, I´m a fan of Ein and I don´t hate Tengu at all, but like I said above, you have to see at TN side.